1. Field of the Invention
The present invention relates to a semiconductor pressure sensor for detecting a pressure of a medium to be measured.
2. Description of the Prior Art
As a device for detecting a pressure of a medium to be measured there has been known a diaphragm type pressure transducer which makes use of a characteristic of a semiconductor which changes its resistance in accordance to an intensity of a pressure as disclosed in Japanese Laid Open Patent Publication No. 1983-63826. There are, however, a number of disadvantages associated with such a transducer. That is, when the diaphragm type pressure transducer is employed for a high pressure medium to be measured, a diaphragm portion is subjected to a high pressure and suffers its peeling off from a support plate and also a damage.
As an improved one for measuring such a high pressure medium, it is known that a pressure sensor disclosed in Japanese Laid Open Patent Publication No. 1987-293131 is available. As shown in FIG. 14, the pressure sensor is provided with a stick-like sensing portion 52 disposed in a cylindrical metal housing 51 and a sealing plate 53 which seals between the sensing portion 52 and the cylindrical housing 51. The sensing portion 52 is provided at its leading end part with a diaphragm portion 54 for detecting a pressure. But, the sensor is disadvantageous in the unpractical construction because the sensing portion 52 is made up of a ceramic material against a recent trendy in which a sensing portion of a pressure sensor is made up of silicon and glass. Even though the sensing portion made us of silicon and glass is employed instead of the sensing portion 52 made up of the ceramic material. It is difficult to keep an airtight condition between the metal housing and the sensing portion made up of silicon and glass.